Sweep and range circuit



y 1952 E. F. M NICHOL, JR 2,597,353

SWEEP AND RANGE CIRCUIT Filed March 22 ,1945

I0 TRIGGER IN FIG. I

I2 I ll l6 I I7 I f I SHUT-OFF SWEEP L INVERTER D c FT' TUBE GENERATOR V RESTORER NEUTRAL- IzING NET WORK I4 27 2 2| 2 CATHODE RAY RANG STEP STEP DEFLECTION TUBE INDICATOR CONTROL AMPLIFIER AMPLIFIER I5\ 24 22 L-VIDEO IN PULSED k PI P OSCILLATOR GENERATO FIG. |a

IIo

III

5+ TO VERTICAL DEELECTION PLATES TO CATHODE OF CATHODE RAY TUBE TO RANGE MARK GENERATOR INPUT TRIL EGER L 7 TO HORIZONTAL 1 DEFLECTION PLATES INVENTOR.

TO RANGE INDICATOR EDWARD EMAC N/CHOL,JR

ATTORNEY Patented May 20, 1952 SWEEP AND RANGE CIRCUIT Edward F. MacNichol, Jr., Wenham, Mass, as-

signor, by mesne assignments, to the United States of America as represented by the Secretary of War Application March 22, 1945, Serial No. 584,230

4Claims. (o1. 25o27) The invention in general relates to electrical circuits and more particularly. to radio circuits.

Radio circuits have been developed that will measure the distance to a target by measuring the time that elapses between the time a pulse is transmitted from the radio set and the time that a portion of the energy reflected from a target returns to the radio set. Several means have been devised for measuring and indicating range in miles or yards to the desired targets. Some systems have been developed that indicate the range to the target on a suitable scale or meter when a pip or range step is made to coincide with the target pip on the scope.

The chief disadvantage with the systems known to the prior art is that a separate range system is necessary, and this system often requires many circuit elements and adds greatly to .the complexity, weight, and size of a radio set. In many applications, such as air-borne or portable operation, weight and size are extremely important factors in the design of a set. In other applications where trained personnel are not available for servicing sets, simplicity is an important factor. I

It is an object-of this invention, therefore, to present a simple, accurate circuit for measuring the range to a target. This circuitwill use a minimum of circuit elements and will present the range data in a convenient usable form.

It is a further object of this invention to present a circuit for producing a gate to be applied to a range mark generator or similar device, a signal to be used in the unblanking of a cathode ray tube, a sweep voltage, and a range step, all of whichsignals'will be synchronized by means of a transmitted pulse and will be derived from the whole or a portion of a sweep voltage generated in this circuit. In accordance with the present invention there is provided a signal generator means that is actuated bya suitable trigger. This signal generator produces a plurality of output voltages having a plurality of wave forms. One of these voltage outputs is fed to a step control circuit. Thisstep control circuit determines; thetime after the input trigger that a pulse will occur in the output of the step control circuit. The output of the step control circuit is fed through suitable amplifiers to squareup the outputwave form'of the step control circuit. r

For a better'unders'tanding of the invention, together with'otlier and further. objects thereof, reference, is had to the following description area in connection with the accompanying 2 drawings, and the scope of the invention will be pointed out in the appended claims. In the accompanying drawings, Fig. 1 is a block diagram of the invention and auxiliary circuits;

Fig. 1A is a view of the cathode ray tube screen and Fig. 2 is a schematic diagram of the invention.

Referring now more particularly to Fig. 1 of the drawings, there is shown in block diagram form the invention and associated circuits arranged so as to form a range indicating system.

A trigger I0 is fed to sweep generator II; this trigger I0 is used to start the sweep generator I l, as will be explained later in connection with Fig. 2. The output of the sweep generator H is fed to a shutoff tube 12, and the output of shutofi tube [2 is fed to the cathode [3 of a cathode ray tube I4, to pulsed oscillator l5 and to sweep generator II. The output of sweep generator H, in addition to going to shutoff tube 12, is fed to direct current restorer I6, inverter ll, neutralizing network I8 and step control 20. The output of step control 20 is fed to step amplifier 2! as is the output of neutralizing network 18. The output of step amplifier 2| is fed through deflection amplifier 22 and thence to deflection plates 23 of cathode ray tube It. The output of pulse oscillator 15 is coupled to pip generator 24. Oscillator l5 and generator 24 together make up a range mark generator. The range marks from pip generator 24 are fed to deflection amplifier 22 where they are mixed with the output of step amplifier 2| and the video signals from a receiver system. A second set of plates 26 in cathode ray tube I4 is fed from inverter I! through direct current restorer I6. Step control 20 in this example is lnechanically coupled to an optical sight 21. The optical sight is not a part of the electrical circuit of the invention, but it serves to illustrate a use of the invention. The use of this circuit with the optical sight will be referred to more fully in connection with the operation of the circuit.

Referring now to Fig. 2, there is shown schematically the circuits more directly related to the invention. The first stage of the circuit is made up of shutoff tube 30 with the'associated plate load resistor 3| and a plate bias circuit made up of resistor 32 and capacitor 33 in parallel. A bias on cathode 34 of tube 3Bis obtained by a voltage divider made up of resistors 36 and 31 connected in series between ground and a source of 3+ potential. Cathode is connected to the point 38 between the two resistors 35 and 31. A bypass capacitor 39 is connected from cathode 34 to ground so that cathode 34 is effectively at ground potential for alternating currents. Anode 4| of tube 39 is coupled to grid 42 of tube 43 by means of a network made up of resistor 44 in parallel with capacitor 46. A coupling capacitor 41 is also connected to grid 42 and serves as a means for applying a trigger 19 to grid 42.

The sweep generator circuit is made up of sweep generator tube 43, a diode 45, and a vacuum tube 50 connected as a cathode follower. The resistance-capacitance combination for producing the saw tooth voltage is made up of resistor connected from cathode 52 of tube 45 to anode 53 of tube 43 and the series combination of capacitor 54 and resistor 56 connected between anode 53 of tube 43 and ground. The point 51 between capacitor 54 and resistor 56 is connected to grid 58 of tube 39, and anode 53 of tube 43 is connected to grid 59 of tube 59. -Resistor 6| is connected between cathode 62 of tube 59 and ground and serves as a cathode load for tube 59. Anodes 63 of tube 59 and '64 of tube 45 are returned to a source of 13-]- potential. A coupling capacitor 66 connects cathode 52 of tube 45 and cathode 62 of tube 59. The circuit as described to this point will be referred to as a signal generator circuit.

The circuit of the block-marked step control 29 in Fig. '1 is made up of vacuum tube 61 and resistors 68, 69, and 15. Resistors 6B and 69 are connected in series between source of positive potential and ground and serve as a voltage divider. Resistor is connected from cathode 16 of tube '61 to a movable tap 11 on resistor 69. The anode 19 of tube 61 is connected to cathode 62 of tube 59.

The output of the step control is coupled to a two stage step amplifier containing vacuum tubes 19 and 19. Resistor BI is the plate load resistor for tube 18, and the parallel combination of resistor 32and capacitor 83 form a cathode bias circuit to maintain cathode 84 of tube 18 at a positive potential with respect to ground. Grid 86 of tube 18 is coupled to cathode 16 of tube 61 by means of coupling capacitor 31 while grid leak resistor 88 is connected between grid '96 and ground. A coupling capacitor 89 connectsanode 99 of tube 18 to a coupling network made up of resistors 95and 99 and capacitor 91. Resistor 96 and capacitor-91 are connected in parallel between grid 98 of tube 19 and one end of capacitor 89. Resistor 85 is connected from this same end of capacitor 69 to a source of 3+ potential. The second stage of amplification consists of tube 19 with its load resistor 99 connected between a source of 3+ potential and anode IN. The cathode N2 of tube 19 is connected to ground. A neutralizing means comprising variable capacitor |93 is connected from cathode62 of tube 59 to grid 98 of tube 19.

Means are provided for taking signals from this circuit at the following points:

The range step at anode |9| of tube 19.

The cathode ray tube sweep at cathode 62 of tube 59.

The gate for the range mark generator at anode 4| of tube 39, and

The unblanking gate for the cathode ray tube at point I94 between resistors 3| and 32.

The operation of this circuit is as follows. Tube 43 is normally conducting with the grid at or near cathode potential. Tube 39 may be conducting slightly or may be completely out off and grid 58 is at a potential somewhat below that of cathode 34. A negative trigger is applied to grid 42 of tube 43 through coupling capacitor 41. This trigger is supplied at predetermined times and provides a reference time for the entire circuit. When this circuit is used with a radio pulse transmitter to measure distance, the trigger usually occurs at the same time as a pulse is sent out from the transmitter. This negative trigger cuts on" tube 43, and anode 53 attempts to rise to 3+ potential, but it is pre vented from doing this by the fact that capacitor 54 cannot change charge instantaneously. A sudden rise in potential occurs at point 51 due to the initial charging current of capacitor 54 flowing through resistor 56. This rise in potential is transferred to grid 59 of tube 59 and anode 53 of tube 43 by capacitor 54. After this small initial rise, the potential of anode 53 starts to rise exponentially to 3+ at a rate determined by the time constant of the resistance-capacitance circuit comprising tube 45, resistors 51 and 56 and capacitor 54. The sudden rise inpotential at point 51 is applied to grid 58 of tube 39. This causes an increase in plate current in tube 39 which in turn causes the potential of anode 4| to drop. This drop is applied to grid 42 ,of tube 43 to keep this tube cutoff after the negative potential provided by the trigger is removed. The drop in potential at anode 4| is used also as a negative gate to be applied to the range mark generator to cause the generator to become operative. A second negative gate is taken from point I94 and applied to the cathode ray tube in the form of an unblanking pulse. This negative gate differs from the gate taken from anode 4| only by the direct current potential difference produced by the parallel combination of resistor 32 and capacitor 33. The signal on anode 53 pr tube 43 is also applied to grid 59 of tube 59. The same wave form will be present at the cathode 62 of tube 59 as was present on the grid but will be reduced in amplitude by the gain of the cathode follower. This signal is applied to cathode 52 of tube 45 by means of coupling capacitor 66. I g charge until the potential of cathode 5-2 of tube 45 reaches approximately the potential of anode 64. When this point is reached, tube 45 ceases to conduct, capacitor 54 stops charging; and therefore, no current will flow through resistoi 55. Point 51 will beat ground potential; since there is no potential drop across resistor 56, this will cause a drop in plate current in tube 39 due to grid 58 dropping in potential. If the plate current drops in tube '39, thepotential of anode 4| will rise which will mean that grid 42 of tube 43 will rise in potential. The rise in potential on grid 42 causes tube 43 to conduct causing the potential of anode '53 to fall. Capacitor 54 discharges rapidly through tube 43 so the potential of anode 53 will fall much more rapidly than it rises. Once tube 43 conducts, initial conditions are restored, and the cycle will be repeated the next time a negative trigger is applied to grid 42 of tube 43. The rate of rise and the time duration of the exponential voltage at anode 53 may be controlled by proper selection of circuit constants. V V

A voltage to produce a sweep on the cathode ray tube associated with this circuit'may be taken from cathode62 of tube 59. The output of cathode 62, which is essentially a'trapez'oidal wave, is also coupled to anode 19 of diode 61. The cathode 16 of tube 61 is maintained at aposi- Capacitor 54 continues totube 61.

tive potential with respect to ground by means of a voltage divider made up of resistors 88 and '89. The potential of cathode I8 may be varied by varying tap TI on resistor 69. No signal will be applied to grid 86 of tube I8 as long as anode I8 is at a lower potential than cathode 18. Since the signal on anode I8 is a trapezoidal wave, the bias' on cathode 16 of tube 61 Will determine the time that will elapse after the input trigger before a signal will be applied to grid .86 of tube 18. The signal that is applied to grid 88 is essentially a positive-going saw tooth wave. The signal is amplified in tube 18 and it is then applied to grid 98 of tube I9. The coupling circuit comprising capacitors 89 and 91 and resistors 95 and 96 is designed to maintain grid 98 at the proper direct current potential. The signal is amplified in tube 19 and the output to the cathode ray tube is taken from anode I8I of tube 19. Although the signal on grid 86 was a saw tooth, the slope of the output wave is nearly vertical due to the amplification of the two stages. The amplitude of the signal is limited by the point where grid 88 starts to go above cathode potential and where grid 98 of tube 19 goes below cutoff. The resulting output wave from anode I8I of the tube 19 is essentially a rectangular wave, the leading edge of said wave occurring at a time after the start of the sweep determined by the position of tap H on resistor 69. A small variable capacitor I83 is used to neutralize any signal appearing on grid 98 of tube 19 that has been coupled through to this grid by the interelectrode capacitance of Capacitor I83 performs this neutralization by coupling a signalto grid 98 that is in phase opposition to any signal coupled to grid 98 by stray capacitance of tube 61. Capacitor I83 is adjusted for optimum performance of the circuit.

The tap 11 on resistor 89 may be mechanically coupled to a device to read range. This coupling is represented by the dotted line I86. When the step on the cathode ray tube screen is made to coincide with the target pip, the range measuring device can be made to read the range to the target directly; or if desired, the movement of tap TI may be mechanically connected to a device, for example, a sight so that when the range step is made to follow a target pip, the range is set into the device automatically. This second application is illustrated in Fig. 1 of the drawings. Optical sight 21 is mechanically coupled to tap 11 of resistor 69 in Fig. 9. Fig. 1A shows a view of the screen of cathode ray tube I4. A pip I88 on time base I89 indicates the time a pulse of radio frequency energy is transmitted by the system, a second pip II8 indicates the time that an echo is received by the system. Range step III forms a depression in time base I89 as shown in Fig. 1A. As tap TI is moved so as to keep the range step III in coincidence with the target pip N8, the range to the target is automatically set into the sight. The tap 11 on resistor 69 may be moved manually or may be positioned by suitable automatic range tracking circuit.

While there has been described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit 'fixed time relationship with a suitable synchronizing pulse and a second group of voltage wave forms occurring in a variable time relationship with said synchronizing pulse and for controlling and indicating the time relationship between said second group of wave formsand said synchronizing pulse; said circuit comprising a means for introducing a synchronizing pulse, signal generator means responsive to said synchronizing pulse, said generator means comprising an amplifier means, a sweep generator means, and a cathode follower means; a step control means, said step control means comprising a vacuum tube and a source of variable direct current potential; a step amplifier means comprising two stages of amplification; means for applying at least a portion of the output of said signal generator means to said step control means; means for applying at least a portion of the output of said step control means to said step amplifier means; a neutralizing means for applying at least a portion of the output of said signal generator means to at least one stage of said step amplifier means; and means associated with said source of variable direct current potential for indicating time relationship between the output of said step amplifier and said synchronizing pulse.

2. A signal generator circuit for producing a first group of voltage wave forms occurring in a fixed time relationship with a suitable synchronizing pulse and a second group of voltage wave forms occurring in a variable time relationship with said synchronizing pulse: and for controlling and indicating the time relationship between said second group of wave forms and said synchronizing pulse, said circuit comprising a means for introducing a synchronizing pulse; a signal generator means responsive to said synchronizing pulse; a step control means comprising a vacuum tube and a source of variable direct current potential; means for applying a portion of the output of said signal generator means to said step control means; means associated with said source of variable direct current potential calibrated to indicate the time relationship between the output of said step control circuit and said synchronizing pulse; an amplifier means, and means for applying at least a portion of the output of said step control means to said amplifier means.

3. A signal generator means for producing a plurality of voltage pulses, the start of said voltage pulses being determined by a synchronizing pulse and the end of said voltage pulses being determined by voltage relationships within said signal generator means, said circuit comprising a means for introducing a synchronizing pulse, a trapezoidal generator means responsive to said synchronizing pulse, an amplifier means, a cathode follower means, means for applying at least a portion of the output of said trapezoidal generator means to said amplifier means and said cathode follower means, means for applying at least a portion of the output of said amplifier means to said trapezoidal generator means, and means for applying at least a portion of the output of said cathode follower means to said trapezoidal generator means, said last mentioned means comprising a capacitor and a vacuum tube.

4. A signal generator circuit for producing a plurality of wave forms occurring in a fixed time 7 relationship with a synchronizingpulse, sai'd circuit comprising a means iorintroducing a synchronizing pulse, a trapezoidal generator means responsive to said synchronizing pulse, an amplifier means, a cathode follower means, means for applying at least a portion of the output of said trapezoidal generator means to said amplifier means and said cathode follower means, means for applying at least a portion of the output of said amplifier means to said trapezoidal generator means, and means for applying at least a portion of the output of said cathode follower means to said trapezoidal generator means.

EDWARD F. MACNICHOL, JR.

REFERENCES CITED The following references are of record in the file of this patent:

STATES PATENTS 

